The present invention relates to communication networks.
It is proposed to improve distributed resource allocation in Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication networks.
The invention is developed with specific attention paid to its possible use in Mobile Wireless Broadband Access networks conforming to IEEE std 802.16-2004 as amended by IEEE 802.16e-2005 and IEEE 802.16g. The current reference texts for the standards mentioned in the foregoing are the following:                IEEE Computer Society and IEEE Microwave Theory and Techniques Society, “IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems”, IEEE Std 802.16-2004 (Revision of IEEE Std 802.16-2001), 1 Oct. 2004;        IEEE Computer Society and IEEE Microwave Theory and Techniques Society, “IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems” Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1, 28 Feb. 2006; and        IEEE Computer Society and IEEE Microwave Theory and Techniques Society, “Draft IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems—Management Plane Procedures and Services”, IEEE P802.16g/D7, January 2007.        
Further exemplary of networks are Mobile WiMAX networks, based on the IEEE 802.16 specifications.
The current reference texts for the Mobile WiMAX networks are the following:                WiMAX Forum, “WiMAX End-to-End Network Systems Architecture (Stage 2: Architecture Tenets, Reference Model and Reference Points)”, Revision 1.0.0: 2007-03-09, draft;        WiMAX Forum, “WiMAX End-to-End Network Systems Architecture (Stage 3: Detailed Protocols and Procedures)”, Revision 1.0.0: 2007-03-09, draft.        
WiMAX Forum, based on IEEE 802.16 specifications, assign to Radio Resource Management (RRM) the tasks of measurement, exchange, and control of radio resource-related indicators (e.g., current subchannel allocations to service flows) in the wireless network. RRM related signalling is realized by two functional entities within RRM: the Radio Resource Control (RRC) functional entity and Radio Resource Agent (RRA) functional entity.
As expressly indicated by the WiMAX Stage 2 specification, the control function primarily refers to decisions made by a measuring station or remote entity to adjust (i.e., allocate, reallocate or de-allocate) radio resources based on the reported measurements and other information, or by using proprietary algorithms, and communicating such adjustments to network entities using standardized primitives. Such control may be local and remote from the measuring station.
WiMAX forum architecture specifications define the network elements where Access Service Network (ASN) functions are located. In particular, Section 14.2.6 “Radio Resource Management” of IEEE 802.16g/D7 specification describes the set of primitives for supporting RRM procedures between a Base Station (BS) and Network Control and Management System (NCMS). Since NCMS, or part of it, can be located in a BS, RRM primitives also permit direct BS-to-BS communication, which can be exploited in case of distributed RRM profile. A RRM network profile is considered hereafter. In this network profile radio resources (e.g. Permutation Zones, available subchannels) are not allocated by a central controller which coordinates several BSs but by individual BS RRM functions. At present time, IEEE 802.16g specification allows BSs to exchange RRM related information by RRM Request and Response primitives: C-RRM-REQ and C-RRM_RSP. Any time an updated information is needed, Radio Resource Control (RRC) entity in the BS can send to all neighbor BSs the message C-RRM-REQ (Action_Type==Spare Capacity Report). Neighbor BS replies with C-RRM-RSP (Action_Type==Spare Capacity Report), providing details concerning the allocated Permutation Zones.
Since allocation of Permutation Zones is controlled by local BS RRM in a distributed RRM profile, very frequent message exchange is needed among neighbor BSs to make sure the information is updated. As a consequence, high signalling load is generated.
Besides, at the present stage, there is no way that a BS can use to inform neighbor BSs which subchannels are reserved or preferred for transmission at the BS. Hence collisions to Co-Channel interference (CCI) and Adjacent Channel Interference (ACI) among neighbor BSs cannot be avoided. As a consequence, in a distributed RRM network profile, interference management among neighbor BSs cannot be operated in a proper way.